The coding issue is not a problem, as many think. What does the game need to know, after all? All it needs to record are the parents of each villager - which it already does, at least up to adulthood. Compare the two villagers in the match you're trying to make and check to see if they share a parent. Not exacting enough? Then check the parent's parents as well. With a couple of other checks, this could provide a complete denial of inbreeding. The game could follow this chain of data as far back as it has data, without ever having to store more information than who the parent of each villager is.

Program complexity is not an issue. Amount of data is not an issue. And as Complexity said himself, (herself?) it's not an issue I want to see in a game. Complexity's own words imply that Complexity wouldn't ever have bothered to think about it if not for posts in the forums, just as I never bothered to before coming here.

Lastly, LDW did not achieve an "E for Everyone" rating on Virtual Villagers due to themes that I suspect are related to their depiction of baby-making - it's for ages 6+ as things stand. Do you really think it would remain suitable for ages 6 and up if they had references to inbreeding right in their options menu?

We already have enough difficulty ensuring a village's survival. I think the suggestion of being able to make exclusive couples - or marrying villagers, if you'd like to put it that way - is more than enough to deny any inbreeding if a player doesn't like it, and also is a tool for those who are trying to breed for certain types of villagers. You also don't have to put an "Inbreeding on/off" switch in the menu.